Aircraft design entails consideration of a myriad of details. A non-limiting list of some details includes size, capacity, weight, range, payload, speed, aerospace standards, airport limitations and governmental regulations. In one design aspect, it is generally accepted that aircraft weight (without payload) and aerodynamic drag correlate with aircraft fuselage surface area and correspondingly with aircraft cross sectional perimeter. It is desirable to reduce both weight and aerodynamic drag because greater aircraft weight and/or drag reduces payload and/or range, and higher aerodynamic drag in flight translates into higher fuel usage, and also translates into higher carbon dioxide emissions, all other factors being equal. Aerodynamic drag increases as the lateral cross sectional area increases because perimeter is related directly to cross sectional area for a fuselage shape. However, the larger the aircraft lateral cross sectional area, the more spacious the interior of the aircraft for passenger comfort. Accordingly, a balance is struck between interior space (which translates to cross sectional area) on the one hand and weight and aerodynamic drag on the other. With increasing fuel costs, reduction in aircraft fuselage perimeter and cross sectional area is becoming more desirable.
Aircraft cross sectional area correlates to the perimeter of the fuselage at any point along the length of the aircraft. Fuselage perimeter in turn correlates with the width of the fuselage. Accordingly, one approach to conserving fuel is to reduce fuselage width, while maintaining passenger comfort.
Typically, aircraft design commences with consideration of interior requirements such as number of aisles, number of seats and how these are grouped in rows and columns, service areas, storage areas (e.g., overhead bins), checked-in baggage compartments, and the like. Once the parameters defining these requirements have been met with an interior design, a fuselage may be designed to envelope the interior design. The fuselage is typically constructed with a fuselage skin structurally connected to a skeleton structure that includes a series of spaced-apart, hoop-shaped frames that define the aircraft cross section at locations along the length of the fuselage. Thus not all frames are identical; if the aircraft tapers from central section to tail section, for example, then frames near the center of the aircraft may be larger hoops and successive frames will decrease in hoop size and the hoop shape of the frame may also change, moving aft to the tail section. Frame spacing may vary, but is typically in the range 18 to 25 inches apart. These frames are covered with an aircraft skin, typically made up of skin panels, typically provided with adjacent stiffening stringers, to produce the outer shell of the fuselage that encloses the interior. Stringers or longerons may also be provided to act with the skin and frames. A cabin is formed inside the fuselage by supplying a floor, a ceiling and covering the interior sides of the fuselage with decorative interior panels.
An example of a prior art cabin interior 10, omitting the storage bins and areas above the ceiling and below the floor, is illustrated in lateral cross section in FIG. 1. The cabin 10 is surrounded by a fuselage 22 that is supported by hoop-shaped frames 20 that are 6 inches (152.4 mm) thick in this example. The seating in cabin 10 is laid out in a two-aisle (12, 14) arrangement. Seats 30, 32 are located at the right side of aisle 14, seats 33, 34 and 35 in the center, and seats 36, 37 that are located to the left of aisle 12. The most outboard seats, or “window seats,” 32, 36 have 2 inch (5.1 mm) wide outboard armrests 40, each spaced a distance of 0.5 inches from the respective interior panels, 52, 56. In this case, the fuselage width 60 is 197 inches (500.4 mm) based on: frames 6 inches (152.4 mm) wide, seats 18.5 inches (47 mm) wide, adjacent seats 2 inches (5.1 mm) apart, armrests 2 inches (5.1 mm) wide, aisles 17.25 inches each, and seats 36 and 32 each spaced a distance 45 of 0.5 inches (6.3 mm) from its adjacent interior paneled surface 56 and 52, respectively. Variations are possible based on changes in aisle width, seat width, and other dimensions specified above.
While the interior design of FIG. 1 is efficient, it has disadvantages as well. For example, window spacing is determined by frame location because windows are located between adjacent frames. Typical frame pitch may be about 24 inches so that window pitch is also about 24 inches. But seat pitch may be 32 inches. As a result, when the seats are arranged independently of frame spacing limitations on window location, some passengers with “window seats” may not have a window located in an ergonomically appropriate location for viewing.
Accordingly, it is desirable to develop an aircraft fuselage that is more congruent with a selected interior design of the aircraft to provide a smaller fuselage perimeter as compared to the prior art. In addition, it is desirable to integrate the aircraft fuselage frame structure design with the interior design and window placement to provide a better passenger environment. Furthermore, other desirable features and characteristics of the reduced-perimeter aircraft will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.